1. Field of the invention
This invention relates generally to semiconductor fabrication technology, and, more particularly, to a method for process monitoring during semiconductor fabrication.
2. Description of the Related Art
There is a constant drive within the semiconductor industry to improve the quality and reliability of integrated circuit devices, e.g., microprocessors, memory devices, and the like. Accordingly, the technologies underlying semiconductor processing tools have attracted increased attention over the last several years, resulting in substantial refinements. However, despite the advances made in this area, many of the processing tools that are currently commercially available suffer certain deficiencies. In particular, such tools often lack advanced process data monitoring capabilities, such as the ability to provide historical parametric data, as well as event logging, real-time graphical display of both current processing parameters and the processing parameters of the entire run, and remote monitoring.
These deficiencies can engender nonoptimal control of critical processing parameters, such as processing temperatures, mechanical tool parameters, film composition, and the like. This variability manifests itself as within-run disparities, run-to-run disparities and tool-to-tool disparities that can propagate into deviations in product quality and performance, whereas an improved monitoring and diagnostics system for such tools would provide a means of monitoring this variability, as well as providing means for optimizing control of critical parameters. Further, effective control of a process like chemical mechanical planarization (CMP) can be used to compensate for variability introduced in previous steps such as variation in deposited dielectric film thickness.
Currently, chemical mechanical planarization (CMP) tools that use endpoint detection rely either on (1) laser interferometry or (2) the difference in frictional properties of the various layers in the device (giving rise to measurable changes in the required motor drive current). Neither method is adequate to repeatably and accurately signal an endpoint within a single layer, for example, if one wants to polish only half-way through a silicon dioxide (SiO2) layer. Currently, endpoint detection is not generally used for such tasks. Instead, send-ahead test wafers are typically used to determine optimum polish times for a given lot, reducing tool throughput and increasing manufacturing costs.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided, the method comprising planarizing a dielectric layer disposed above a structure layer, exciting surface plasmons in a conductive film disposed in the dielectric layer and detecting photons reflected from the conductive film to determine a change in a surface plasmon resonant angle. The method also comprises determining a thickness of the dielectric layer from the change in the surface plasmon resonant angle.
In another aspect of the present invention, a device is provided, the device comprising a conductive film disposed in a dielectric layer, the conductive film capable of having surface plasmons excited therein, and a detector adapted to detect photons reflected from the dielectric layer to determine a change in a surface plasmon resonant angle. The method also comprises an endpoint detector adapted to detect the endpoint in planarization based on the determination of the change in the surface plasmon resonant angle.